Question

Say I have an object someObject and an NSMutableArray *someArray. I’m not sure if someObject is in the array, but if it is, I want to remove it. There are two options:

Case 1:

if([someArray indexOfObject:someObject] != NSNotFound)
   [someArray removeObject:someObject];

Case 2:

[someArray removeObject:someObject];

In case 2, if the object doesn’t exist in the array, nothing happens. My question is, is case 2 more efficient, since in case 1 I’d have to search the array and see if it exists, and if it does, I remove it, but I’m guessing removeObject: searches the array again for that object?

Answer 1

but I’m guessing removeObject: searches the array again for that object?

Well, yes, it has to. There’s no way to find an object in a collection without looking for it.* The docs even say this:

This method uses indexOfObject: to locate matches and then removes them by using removeObjectAtIndex:. […] If the array does not contain anObject, the method has no effect (although it does incur the overhead of searching the contents).

You can of course imitate the framework and use removeObjectAtIndex: yourself right after the search if you want.

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_{*This is faster than it might be (at worst O(log(N)) rather than O(N)) because NSArrays aren’t arrays.}